An audio perspective over predictive HCI models

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In our everyday life we perform pointing tasks hundred times a day. These tasks are very different according to the purpose of the gesture. We might be quite accurate and fast when we are putting a stamp on a precise place of a number of documents, while we might be just fast and less accurate when we are indicating the direction to take in a crossing. There are many examples of pointing tasks, and each of them is characterized by a precise feedback (visual, haptic or auditory) and by a precise trade off between accuracy and speed. This thesis concentrates in particular on Fitts’ tasks performed under continuous auditory feedback: it hypothesizes the influence of the feedback on velocity profiles and explores possible transpositions of Fitts’ parameters in the auditory domain. The thesis is organized in 7 chapters. The first chapter (cf. 1) introduces the history of the field which constitutes the background of this thesis, starting from the definitions of Human Factors and its historical links with Human-Computer Interaction discipline. Focusing on this branch of the computer science the relationship with Human Performance and Human Information processing is described. Some predictive models used in HCI are presented as a conclusion of the chapter. This short presentation introduces the second chapter, (cf. 2) which is devoted to the discussion of some predictive HCI models, in particular Fitt’s law, Schmidt’s law and the steering law. All these predictive models are used to evaluate the user performance with particular interfaces — visual interfaces in the large majority of cases. In the first part of the chapter the origins of Fitts’law and its appearence inside the Information theory are presented. Through the discussion of the main aspects under debate is then described the formultion of the law that is currently adopeted in the ISO9621. Different derivation of the law are then reported with the main formulation that have been developed along the years of Human Performance research. Particular attention is given to the deterministic iterativecorrection model, the impulse variability model and the optimized initial impulse model. Shifting from the literature in Human Performance to the one in Human Computer Interaction the last part of the chapter is devoted to the main topics still under discussion on Fitt’s law, the open problems and the main achievements of the last years of research. A presentation of Schmidt’s law and of the steering law conclude the chapter. Chapter three (cf. 3) is devoted to the interface/control part: focusing on the audio domain, it explains what an interface is and how audio feedback can be used beyond the design of musical instruments. Different control metaphors are introduced as well as a definition of gesture. The gesture of the user is the means to produce audio feedback and the gesture that is analyzed in this thesis is a typical Fitts’ task–like gesture. The literature of the “sounding gesture” is discussed through the the main european projects that in the last years studied in different perspective the conjunction of gesture and sound, taking into account two different aspects: the control and the expressiveness. Chapter four (cf. 4) explores how audio feedback has been used to date in interface design in Human-Computer Interaction: starting from the auditory display research about auditory icons and earcons through the new field of research on interactive sonification if naturally reaches the literature on the specific topic of the thesis wich is the use the auditory feedback in conjunction with Fitts’ law studies. The main achievements in this respect are summarized there including the open problems that this thesis has set to address. Chapter five (cf. 5) and six (cf. 6) are devoted to experiments: in particular, chapter five describes four different experiments with four different interfaces. These experiments allow to draw some conclusions and to suggest further experiments. A couple of final experiments are then summarized in chapter 6. The data analysis of these tests drives the conclusions of chapter seven (cf. 7) with which this work ends.